An adaptive braking system is responsive to an imminent skidding condition during braking to relieve the pressure within a wheel cylinder thereby avoiding a lockup of a wheel monitored by the system. When the imminent skidding condition is no longer present, a modulator valve within the system is actuated by a control unit to open communication between the wheel cylinder and a brake booster so that braking is repeated.
The modulator valve controls the fluid communication between the brake booster and the wheel cylinder so that the fluid pressure within the wheel cylinder is decreased when skidding is imminent and increased when the skidding condition is terminated as measured by an electronic control unit.
In a common fluid braking system wherein the same fluid flows from a pressure source to the wheel cylinder, it is desirable to control the fluid pressure level within the wheel cylinder when a skidding condition is imminent and when fluid pressure is communicated to the wheel cylinder after the imminent skidding condition. Such controlled fluid pressure within the wheel cylinder not only avoids pressure surges when fluid is recommunicated to the wheel cylinder after the latter is relieved of fluid pressure, but also provides an even resistance to brake pedal movement so that the operator feels constant resistance during braking regardless of the operation of the modulator valve.